Abstract
Variants of the prototype Alphavirus, Sindbis (SINV), were used in per os infections of adult female mosquitoes to investigate arbovirus interaction with the salivary gland (SG). Infection of Aedine mosquitoes with AR339, a heparan sulfate proteoglycan (HSPG)-dependent variant, resulted in gross pathology in the SG lateral lobes while infection with TR339, a HSPG-independent variant, resulted in minimal SG pathology. HSPG was detected in the internal ducts of the SG lateral lobes by immunolabeling but not in the median lobe, or beyond the triad structure and external ducts. Reports that human lactoferrin interacts with HSPG, suggested an interference with virus attachment to receptors on vertebrate cells. Pre-incubation of Aedes albopictus cultured C7-10 cells with bovine lactoferrin (bLF) followed by adsorption of SINV resulted in earlier and greater intensity of cytopathic response to TR339 compared with AR339. Following pre-treatment of C7-10 cells with bLF, plaques from tissue culture-adapted high-titer SINVTaV-GFP-TC were observed at 48 h post-infection (p.i.), while plaques from low-titer SINVTaV-GFP-TC were not observed until 120 h p.i. Confocal optics detected this reporter virus at 30 days p.i. in the SG proximal lateral lobe, a region of HSPG-immunolocalization. Altogether these data suggest an association between SINV and HSPG in the host mosquito.
Highlights
Arthropod-borne-viruses are etiologic agents that contribute to significant diseases in humans and other animals
Cytopathology in the lateral lobes (LL) of the salivary gland (SG) following intrathoracic inoculation with Sindbis virus (SINV) has been documented in Ae. albopictus [16] and these results were reproduced in per os infections of
The median lobe (ML) remained intact without pathology, in response to virus variants and all mosquitoes used for Figure 1B&C had positive cytopathic effect (CPE) leg-assays indicative of virus dissemination
Summary
Arthropod-borne-viruses (arboviruses) are etiologic agents that contribute to significant diseases in humans and other animals. Sindbis virus (SINV), transmitted by hematophagous female mosquitoes, has caused outbreaks in humans every seventh year in Northern Europe [1] and can cause Pogosta disease, a systemic infection in humans resulting in arthritis, itching rash, fatigue, mild fever, headache, and muscle pain [2]. A member of the genus Alphavirus in the family Togaviridae, SINV is an enveloped virus with a plus-sense, single-stranded, 11.7 kb RNA genome [3]. In addition to being isolated from various insects and vertebrates in Northern Europe, SINV has been found in South and East Africa, Egypt, Israel, the Philippines, and parts of Australia [4]. Replication of arboviruses in the mosquito host is essential for virus persistence, and a horizontal cycle is the primary mechanism of Alphavirus maintenance in nature [8]. Lack of evidence for a vertical transmission route for SINV indicates that feeding physiology of female mosquitoes is integral to arbovirus transmission
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